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doi:10.2204/iodp.proc.340.103.2013

Physical properties

We measured physical properties from 0 to 4.7 mbsf at Site U1393, with the uppermost 2.6 mbsf providing the most reliable values. For the uppermost 4 m, magnetic susceptibility, grain density, P-wave velocity, and bulk porosity are consistent with expectations for moderately to well-sorted sands with an andesite bulk composition. Full core density and P-wave velocity agree well with single spot values made on the split core.

Results

Whole core

We measured magnetic susceptibility, gamma ray attenuation (GRA) bulk density, compressional wave velocity, and natural gamma radiation (NGR) on all core sections (Fig. F2), including those with water, air pockets, and loose clasts. We have no thermal conductivity measurements in Hole U1393A because the sediment was too coarse and its high permeability prevented reliable and meaningful measurements from being made. Of the 4.36 m recovered in the first core (340-U1393A-1H), depths between the core top and 2.6 m are free of gas and water pockets and thus provide the most accurate values. Magnetic susceptibility has a maximum value of 2550 × 10^–5 SI at 1.07 mbsf. Mean P-wave velocity is 1750 m/s. Mean GRA density is 2.0 g/cm³. NGR is typically around 13 counts per second (cps).

We used the handheld penetrometer to measure shear strength values of 1.35 and 1.16 kPa at 4.36 and 12.8 mbsf, respectively. Peak shear strength measured by the automated vane shear apparatus at 3.6 mbsf is 3 kPa (Fig. F2). This value is not representative of in situ shear strength because the material in the core is sandy and too permeable for measurements to be made at undrained conditions.

Split core

We obtained one discrete P-wave velocity measurement of 1780 m/s at 2.09 mbsf (Fig. F2; red circle). This value coincides with the value recorded by the P-wave logger on the full core. We collected two moisture and density measurements on samples at 0.75 and 3.25 mbsf. Mean values are as follows: bulk density is 2.06 g/cm³, grain density is 2.80 g/cm³, and bulk porosity is 42% (Fig. F2). Measurements from both samples are within a few percent of each other.

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